CEN/TC 340 Anti-seismic devices. CEN/TC 340 DOC. N. 82 June TO DECIDE: X 2 SUBJECT/TITLE

Transcription

1 CEN/TC 340 Anti-seismic devices EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG CEN/TC 340 DOC. N. 82 June TO DECIDE: X 2 SUBJECT/TITLE pren Anti-seismic devices Clause 4 of the Draft Agenda of the 8 th meeting of CEN/TC 340 (AFNOR Paris, /20) circulated on SITUATION/BACKGROUND - 4 PROPOSAL - SECRETARIAT CEN/TC 340 Via Sannio, 2 I MILANO T EL F AX alberto.galeotto@uni.com

2 CEN/TC 340 Date: TC 340 WI CEN/TC 340 Secretariat: UNI Anti-seismic devices Erdbebenvorrichtungen ICS: Descriptors: Document type: European Standard Document subtype: Document stage: CEN Enquiry Document language: E C:\Documents and Settings\fbrusco\Desktop\TC_340_WI_ (E).doc STD Version 2.2

3 Contents Page Foreword Scope Normative references Terms and definitions, symbols and abbreviations General design rules Rigid connection devices Displacement Dependent Devices Velocity Dependent Devices Isolators Combination of Devices Evaluation of conformity Installation In-service inspection Annex A (informative) Commentaries to Clause 1: Scope Annex B (informative) Commentaries to Clause 4: General design rules Annex C (informative) Commentary to Clause 5: Rigid connection devices Annex D (informative) Categories of devices Annex E (informative) Examples of non-linear devices Annex F (informative) Commentary to Clause 7: Velocity dependent devices Annex G (informative) Commentary to Clause 8 Elastomeric isolators Annex H (normative) Equipment for combined compression and shear Annex I (informative) Examples of sliders Annex ZA (informative) Clauses of this European Standard addressing the provisions of the EU Construction Products Directive Bibliography

4 Foreword This document (TC 340 WI ) has been prepared by Technical Committee CEN/TC 340 Anti-seismic devices, the secretariat of which is held by UNI. This document is currently submitted to the CEN Enquiry. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive(s). For relationship with EU Directive(s), see informative Annex ZA, B, C or D, which is an integral part of this document. 3

5 1 Scope This European standard covers the design of devices that are provided in structures with the aim of modifying their response to the seismic action. It specifies functional requirements and general design rules in the seismic situation, material characteristics, manufacturing and testing requirements, as well as acceptance, installation and maintenance criteria. This European standard covers the types of devices listed in table 1 (see 3.4). NOTE Additional information concerning the scope of this European standard is given in Annex A. 2 Normative references This European Standard incorporates, by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). EN :2000, Structural bearings General design rules. EN , Structural bearings Sliding elements. EN , Structural bearings Spherical and cylindrical PTFE bearings. EN , Structural bearings - Protection. EN 1990:2002, Eurocode Basis of structural design. EN :2004, Eurocode 8: Design of structures for earthquake resistance - Part 1: General rules, seismic actions and rules for buildings. EN :2005, Eurocode 8: Design of structures for earthquake resistance - Part 2: Bridges. EN 10025, Hot rolled products of non-alloy structural steels - Technical delivery conditions. EN , Quenched and tempered steels - Part 1: Technical delivery conditions for special steels. EN , Quenched and tempered steels - Part 2: Technical delivery conditions for unalloyed quality steels. EN , Stainless steels - Part 1: List of stainless steels. EN , Stainless steels - Part 2: Technical delivery conditions for sheet/plate and strip for general purposes. EN , Stainless steels - Part 3: Technical delivery conditions for semi-finished products, bars, rods and sections for general purposes. EN , Hot-rolled products in weldable fine grain structural steels - Part 1: General delivery conditions. EN , Plates and wide flats made of high yield strength structural steels in the quenched and tempered or precipitation hardened conditions - Part 1: General delivery conditions. 4

6 EN , Plates and wide flats made of high yield strength structural steels in the quenched and tempered or precipitation hardened conditions - Part 2: Delivery conditions for quenched and tempered steels. EN , Plates and wide flats made of high yield strength structural steels in the quenched and tempered or precipitation hardened conditions - Part 3: Delivery conditions for precipitation hardened steels. EN 10204, Metallic products - Types of inspection documents. ENV , Execution of steel structures - Part 5: Supplementary rules for bridges. EN ISO 4526, Metallic coatings - Electroplated coatings of nickel for engineering purposes (ISO 4526:2004). EN , Structural bearings Elastomeric bearings. EN , Structural bearings Pot bearings. EN , Eurocode 8: Design of structures for earthquake resistance - Part 1: General rules, seismic actions and rules for buildings. EN , Eurocode 8: Design of structures for earthquake resistance - Part 2: Bridges. ISO 34, Rubber, vulcanized or thermoplastic (all parts). ISO 37, Rubber, vulcanized or thermoplastic - Determination of tensile stress-strain properties. ISO 48, Rubber, vulcanized or thermoplastic - Determination of hardness (hardness between 10 IRHD and 100 IRHD). ISO 188, Rubber, vulcanized or thermoplastic - Accelerated ageing and heat resistance tests. ISO 815, Rubber, vulcanized or thermoplastic - Determination of compression set at ambient, elevated or low temperatures. ISO 898, Mechanical properties of fasteners (all parts). ISO 1083, Spheroidal graphite cast iron - Classification. ISO 3755, Cast carbon steels for general engineering purposes. ISO 4664, Rubber - Guide to the determination of dynamic properties. ISO 6158, Metallic coatings - Electroplated coatings of chromium for engineering purposes. ISO 6446, Rubber products - Bridge bearings -- Specification for rubber materials. 3 Terms and definitions, symbols and abbreviations 3.1 Definitions For the purposes of this European Standard, the following terms and definitions apply activation velocity velocity at which a Shock Transmission Unit (STU) reacts with its design force 5

7 3.1.2 axial force N Ed acting on a device under the design seismic action the maximum value during the action is denoted N Ed,max and the minimum value N Ed,max. The minimum value acting on an isolator may be tensile core element component of a Linear Device (LD) or of a Non-Linear Device (NLD) on which the mechanism characterising the device s behaviour is based NOTE Core elements of a LD or of a NLD are the device s components that provide it with the flexibility and, eventually, with the energy dissipation and/or re-centring capacity or any other mechanical characteristic compatible with the requirements of a LD or of a NLD. Examples of core elements are steel plates or bars, shape memory alloy wires or bars, rubber elements design displacement d bd (of a device) displacement (translation or rotation) that a device shall undergo when the structural system is subjected to the design earthquake according to EN (maximum) displacement of a device in a principal direction d Ed for a bridge isolator d Ed equals d max, the maximum total horizontal displacement at the location of the isolator including all actions effects and the application of the reliability factor to d bd, according to EN1998-2, (2)P. For devices in other structures d Ed equals γ x d bd, the design displacement increased by the reliability factor design force V Ebd (of a device) force (or moment) corresponding to d bd devices elements which contribute to modify the seismic response of a structure by isolating it, by dissipating energy or by creating permanent or temporary restraints via rigid connections. The devices considered are described in the various clauses of this European Standard ductility demand (of a device) the displacement ductility demand referred to the theoretical bilinear cycle, and is evaluated as d bd /d 1 (see and ) NOTE The ductility demand is a useful parameter to evaluate the plastic demand of an EDD based on material hysteresis (see ) effective damping (of a device) ξ effb value of the effective viscous damping, corresponding to the energy dissipated by the device during cyclic response at the total design displacement: ξ effb = W(d bd ) /(2π V Ebd d bd ) (1) W(d bd ) = energy actually dissipated by a device during the 3 rd load cycle, with maximum displacement equal to d bd. 6

8 NOTE ξ effb is introduced for a simple characterisation of the behaviour of any device. It cannot be used in the analytical calculations of the response of the structural system, unless it can be carried out by linear analysis and all the devices have the same damping and stiffness in the given direction. Where different devices are used, reference shall be made to the overall effective damping of the isolation system effective period T eff in the case of seismic isolation, is the period of a single degree of freedom system moving in the direction considered, having the mass of the superstructure and the stiffness equal to the effective stiffness of the isolation system effective stiffness of a device in a principal direction K effb ratio between the value of the total horizontal force transferred through the device at the total design displacement in the same direction, divided by the absolute value of the total design displacement (secant stiffness) K effb = V Ebd /d bd (2) NOTE K effb is introduced for a simple characterisation of the behaviour of a device. It cannot be used in the analytical calculations of the response of the structural system, unless it can be carried out by linear analysis and all the devices have the same damping and stiffness in the given direction. Where different devices are used, reference shall be made to the overall effective stiffness of the isolation system effective stiffness of an isolation system in a principal direction K eff sum of the effective stiffness of the devices located at the isolation interface effective stiffness centre stiffness centre of an isolation system, accounting for the effective stiffness of the devices energy dissipation design a design approach in which mechanical elements are introduced at certain locations of the structure to dissipate the energy which is introduced into the structure by an earthquake energy dissipation capacity ability of a device to dissipate energy during the load-displacement cycles energy dissipating device (EDD) a device which has a large energy dissipation capacity, i.e. which dissipates a large amount of the energy stored during the loading phase. After unloading it normally shows a large residual displacement. A device is classified as EDD if the equivalent viscous damping ξ is greater than 15% first branch stiffness K 1 of a NLD the initial stiffness of a NLD is defined as the secant stiffness between the points corresponding to the forces V Ebd /10 and V Ebd /5: K in = (V Ebd /5 V Ebd /10) /(d(v Ebd /5) - d(v Ebd /10) (3) 7

9 NOTE K 1 is referred to as initial or elastic stiffness when dealing with softening devices Fluid Viscous Damper (FVD) an anti-seismic device whose output is an axial force that depends on the imposed velocity only; its principle of functioning consists of exploiting the reaction force of a viscous fluid forced to flow through an orifice and/or valve system Fluid Spring Damper (FSD) an anti-seismic device whose output is an axial force that depends on both imposed velocity and stroke; its principle of functioning consists of exploiting the reaction force of a viscous fluid forced to flow through an orifice and/or valve system and at the same time is subjected to progressive compression Hardening Device (HD) a NLD whose effective stiffness K effb and second branch stiffness K 2 are greater than the first branch stiffness K Hydraulic Fuse Restraint (HFR) Hydraulic Fuse Restraints are SRs whose behaviour is hydraulic in nature and depends upon the opening of relief valves stiffness K in of a LD the stiffness of a LD is defined as the secant stiffness between the points corresponding to the forces V Ebd /10 and V Ebd /5: K in = (V Ebd /5 V Ebd /10) /(d(0,2 V Ebd ) - d(0,1 V Ebd ). (4) NOTE The evaluation of K in as secant stiffness is justified by the difficulty of tracing the tangent to a curve at the origin in an experimentally drawn diagram isolation system the collection of devices used for providing seismic isolation isolation interface in the case of seismic isolation, the surface which separates the substructure and the superstructure and where the isolation system is located isolator a structural bearing possessing the characteristics needed for seismic isolation, namely, ability to support gravity load of superstructure, and ability to accommodate lateral displacements. Isolators may also provide energy dissipation, and contribute to the isolation system s re-centring capability linear device (LD) an anti-seismic device which is characterised by a linear or almost linear load-displacement relationship up to the displacement d bd, with a stable behaviour under a large number of cycles and substantial independence from velocity. After unloading, it does not show a residual displacement. Even when some energy dissipation occurs in the device, residual displacements shall be negligible, and in any case less than 2% of the maximum displacement 8

10 NOTE For visco-elastic devices, residual displacements can be partially or totally recovered after some hours. In this case, the final residual displacement should be referred to Mechanical Fuse Restraint (MFR) an SR whose behaviour is determined by the break-away of sacrificial components Non Linear Device (NLD) an anti-seismic device which is characterised by a non linear load-displacement relationship, with a stable behaviour under the required number of cycles and substantial independence from velocity. A device is classified as non linear if either ξ effb is greater than 15% or the ratio K effb -K 1 /K 1 is greater than 20%, where ξ effb and K effb are evaluated at the 3rd cycle with maximum displacement equal to d bd Non-linear Elastic Devices (NLED) an NLD which normally dissipates a negligible amount of the energy stored during the loading phase. The static residual displacement after unloading shall be negligible. A device is classified as NLED if ξ effb is less than 15% while the ratio K effb -K 1 /K 1 is greater than 20% Figure 1 Initial and effective stiffness of a linear device Figure 2 Effective stiffness of a non linear device. 9

11 Permanent Connection Device (PCD) a device which provides steady restraint in one or two horizontal directions, accommodates rotations and vertical displacements, i.e. does not transmit bending moments and vertical loads; the device which restrains the movements in one horizontal direction only is referred to as Moveable Connection Device, while the device which restrains the movements in two horizontal directions is defined as Fixed Connection Device. NOTE In certain circumstances the above devices may be required to operate in a plane inclined to the horizontal. In such event the terms "vertical" and "horizontal" take on the appropriate significance Rigid Connection Device (RCD) a device which links two structural elements without transmitting bending moments and vertical loads; this category of devices includes Permanent Connection Devices (see 5.1), Fuse Restraints (see 5.2) and Temporary Connection Devices (see 5.3) Sacrificial (Fuse) Restraint (SR) a device that, below a certain pre-established force threshold (break-away force), impedes any relative movements between connected parts, whilst it permits the same after the aforesaid threshold has been exceeded second branch stiffness K 2 parameter referred to the theoretical bilinear cycle and defined as (see figure 2): K 2 = (V Ebd - V[d bd /2]) / [d bd /2] (5) where: V[d bd /2]) is the force corresponding to [d bd /2] at the 3 rd cycle of the test. NOTE 1 The formula is obtained by evaluating the second branch stiffness as a secant stiffness referred to displacements d bd /2 and d bd NOTE 2 K 2 is often referred to as post-elastic stiffness when dealing with softening devices seismic isolation a design approach in which appropriate mechanisms (isolation systems) are provided at a certain level of the structure to decouple the part of the structure located above this level, therefore modifying the seismic response of the structure and its contents service life of a device is taken as that given in Technical Specifications of the Project, based on declarations made by manufacturers. NOTE Additional information concerning the service life is given in informative annex B Shock-Transmission Unit (STU) a device whose output is an axial force that depends on the imposed velocity; its principle of functioning consists of exploiting the reaction force of a viscous fluid forced to flow through an orifice in order to provide a very stiff dynamic connection whilst for low velocity applied loads the reaction is negligible Softening Device (SD) a NLD whose secant stiffness K effb and second branch stiffness K 2 are smaller than the first branch stiffness K 1 10

12 Statically Re-centring Device (StRD) an Energy Dissipating Device whose force-displacement cyclic curve at the 3 rd cycle passes through or very near the origin of the axes, at a distance not greater than 0,1 d bd substructure in the case of seismic isolation, the part of the structure which is located under the isolation interface and is anchored to the foundations superstructure in the case of seismic isolation, the part of the structure which is isolated and is located above the isolation interface Supplemental Re-centring Device (SuRD) a device whose force-displacement cyclic curve at the 3 rd cycle passes through or very near the origin of the axes and, for small displacement at unloading [0,1 d bd ], provides a force which is at least 0,1 V Ebd NOTE The supplemental force > 0,1 V Ebd is meant to counteract the effect of parasitic non-conservative forces (e.g. friction in other devices, yielding in structural elements, etc.) or other energy dissipating non re-centring devices, in order to provide the entire structural system with an overall Re-centring capability. The supplemental force is calibrated according to the re-centring requirements of the structural system Temporary Connecting Device (TCD) an anti-seismic device whose output is a force that depends on the imposed velocity; its principle of functioning consists of a system providing for the required reaction force when dynamically activated whilst for slow applied movements it does provide a major reaction theoretical bilinear cycle of a NLD it is conventionally defined to identify the main mechanical characteristics of a non linear device through the first and second branch stiffness values and by the following parameters: d 1 = V 1 = V Ebd = abscissa of the intersection point of the straight line starting at the origin with stiffness K 1 and the straight line passing through (d bd, V Ebd ) with stiffness K 2 in the experimental 3 rd load cycle of a quasi static test; ordinate of the intersection point of the straight line starting at the origin with stiffness K 1 and the straight line passing through (d bd, V Ebd ) with stiffness K 2 in the experimental 3 rd load cycle of a quasi static test; force corresponding to d bd, obtained at the 3rd load cycle during a quasi static test. NOTE In order to use the theoretical bilinear cycle to model a device s behaviour in non-linear simulation analyses of structural systems, the unloading branch of the theoretical cycle should approximate at best the real behaviour of the device. With this aim the value of ξ effb of the theoretical cycle should not differ from the value of ξ effb of the 3 rd cycle of a type test by more than ±10%. 11

13 3.2 Symbols NOTE The list below covers most of the symbols. Others are defined at their first occurrence in the text Latin upper case letters A Area m 2 F Load, force acting on a device MN G Shear modulus MPa M Moment, bending moment MN m N Axial force MN V Shear force MN R Resistance MPa S Acting force, acting moment, shape factor MN, MN m T Temperature, total thickness C, mm E Modulus, energy GPa, MJ K Stiffness of a device MN/m Latin lower case letters a, b Length m d Displacement (translation or rotation) of a device m f Strength, frequency MPa, Hz t Thickness of a layer, tolerance mm x, y Horizontal co-ordinates z Vertical co-ordinates Greek letters α Coefficient of thermal expansion, angle of rotation / C, rad γ Partial safety factors, over-strength factor ξ Equivalent viscous damping factor ε Strain μ Coefficient of friction Subscripts a b c cr d e actual bearing or device compression critical design elastomer 12

14 eff effective, equivalent value at design displacement el elastic h horizontal i i-th cycle, i-th element (generic) in initial k characteristic max maximum min minimum res residual s steel sc secant u ultimate v vertical, velocity x horizontal co-ordinate, increased reliability y horizontal co-ordinate z vertical co-ordinate E related to seismic situation I importance L lower limit of service range M material R resistance value S acting value U upper limit of service range 1 conventional elastic limit, first branch in the theoretical bilinear cycle of a NLD 2 design displacement and force, second branch in the theoretical bilinear cycle of a NLD 3 3 rd cycle φ related to bending 3.3 Abbreviations DP Design properties DRD DSC EDD FR FSD FVD Dynamically Re-centring Device Differential Scanning Calorimeter Energy Dissipating Device Fuse Restraint Fluid Spring Damper Fluid Viscous Damper 13

15 HD HDRB HFR LBDP LD LDRB LRB MFR NDP NLD NLED NRD PCD RCD SD SLS SMA SRCD SRs StRD STU SuRD TCD UBDP ULS Hardening Device High Damping Rubber Bearing Hydraulic Fuse Restraint Lower Bound Design Properties Linear Device Low Damping Rubber Bearing Lead Rubber Bearing Mechanic Fuse Restraint Nationally Determined Parameters Non Linear Device Non Linear Elastic Devices Non Re-centring Device Permanent Connection Device Re-Centring Devices Softening Device Serviceability Limit State Shape Memory Alloys Supplement Re-Centring Devices Sacrificial (Fuse) Restraints Statically Re-centring Device Shock-Transmission Unit Supplemental Re-centring Device Temporary Connecting Device Upper Bound Design Properties Ultimate Limit State 3.4 List of devices Symbols representing the most common type of devices are given in Table 1. 14

16 15

17 4 General design rules NOTE Additional information concerning the general design rules is given in annex B. 4.1 Performance requirements and compliance criteria Fundamental requirements The anti-seismic devices and their connections to the structure shall be designed and constructed in such a way that the following requirements are met, each with an adequate degree of reliability: a) No failure requirement The anti-seismic devices and their connections to the structure shall be designed and constructed to withstand the design seismic action defined in 2.1(1)P of EN without local or global failure, thus retaining their functional integrity and a residual mechanical resistance, including when applicable a residual load bearing capacity, after the seismic event. NOTE The non failure requirement concerns the structure as a whole and, when appropriate, the device and its connection to the structure. It does not concern SRs. b) Damage limitation requirement The anti-seismic devices and their connections to the structure shall be designed and constructed to withstand a seismic action having a larger probability of occurrence than the design seismic action, without the occurrence of damage and the associated limitations of use, the costs of which would be disproportionately high in comparison with the costs of the structure itself. The seismic action to be considered for the damage limitation requirement is defined in 2.1(1)P of EN NOTE Non-seismic design situations covered by this European standard should also be considered Reliability of the structural system Reliability differentiation According to the corresponding parts of EN 1998, reliability differentiation for different types of buildings or civil engineering works shall be implemented by classifying structures into different importance categories. To each category, an importance factor γ I shall be assigned and applied to the seismic action. NOTE Values of the factor γ I are recommended in the corresponding parts of EN Increased reliability According to EN , sub-clause 10.3(2)P, in the case of isolation systems, increased reliability shall be required for the isolation devices and their connections to the structure. NOTE 1 In EN , this is implemented by applying a magnification factor γ x on seismic displacements of each unit. In EN , this magnification factor is called γ IS For devices not used in an isolation system, depending on the role they play in the stability of the construction after the earthquake, a reliability factor γ x equal or greater than 1 shall be applied to the seismic action effects on the devices and their connections to the structure. 16

18 NOTE 2 Recommended minimum values of γ x for isolators are given in EN and EN (where the factor has the symbol γ IS ), and for other devices in the relevant clauses of this European Standard. NOTE 3 Higher values of γ x may be defined by National Authorities or by the owner in the case of a critical structure Functional requirements Devices and their connections to the structure shall be designed and constructed in such a way as to function according to the design requirements and tolerances throughout their projected service life, given the mechanical, physical, chemical, biological and environmental conditions expected. Devices and their connections to the structure shall be designed, constructed and installed in such a way that their routine inspection and replacement are possible during the service life of the construction. NOTE For the enforcement of this requirement, it is necessary that the design of the structure takes account of accessibility for both equipment and personnel Structural and mechanical requirements Devices and their connections to the structure shall be designed and constructed in such a way that their performance characteristics conform with the design requirements, as given below: a) Requirements at the ULS NOTE 1 The verification of the devices at the Ultimate Limit State (ULS) is associated with the design seismic situation, with due consideration of the reliability of the structural system. The devices and their connections to the structure shall be verified, with an adequate degree of reliability, to have an appropriate strength and ductility to withstand actions effects in the seismic design situation, taking into account the importance factor γ I and the reliability factor γ x of the structural system, as defined in 4.1.2, and second order effects. At the ULS, the devices and their connections to the structure can suffer damage, but shall not reach failure except in the case of sacrificial restraints, for which requirements given in 5.2 apply. Replacement of the device after any damage suffered shall be possible without resorting to major intervention. Where applicable, they shall retain a residual capacity at least equal to the permanent actions to which they are directly subjected or to such combinations of actions corresponding to design situations (including eventually a seismic situation) that may occur after the earthquake, as defined by the structural design. b) Requirements at the SLS NOTE 2 The verification of the devices at the Serviceability Limit State (SLS) is associated with the damage limitation requirement and the corresponding seismic action, as defined in At the SLS, the devices and their connections to the structure shall remain in a serviceable state, at least as far as their performance under further seismic loads is concerned, and undergo only very minor or superficial damage which should not induce interruption of use, nor require immediate repair Compliance criteria Performance requirements concerning the devices and their connections to the structure shall be satisfied by complying with the procedures set forth by the corresponding clauses of this European Standard, according to the type of devices used. NOTE The verification of compliance criteria may be obtained by appropriate modelling or testing according to the corresponding clauses of this European Standard. 17

19 4.2 Actions Seismic design situations and seismic combinations of actions The seismic design situations defined in shall be associated with the seismic combinations of actions defined in of EN 1990: Representations of the seismic action The design seismic action shall be that defined in section 3 of EN , using an elastic response spectrum or related accelerogrammes. Whenever a behaviour factor is applicable, a design spectrum shall be used Dynamic analysis According to the types of devices concerned, the dynamic structural analysis shall be performed either by using a response spectrum or by using a time history analysis. The use of a response spectrum in connection with an equivalent linear behaviour shall be ruled by conditions given in clause of EN in particular as concerns limitation of damping. When these conditions are not met, a time-history structural analysis shall be used. NOTE It is strongly recommended that a time-history analysis is performed when the equivalent damping ratio is higher than 15% Effects of actions Combinations of the effects of the components of the seismic action on structures shall be as defined in the corresponding parts of EN Effects of actions on devices and their connections to the structure in the seismic situation shall be determined by the application of the structural analysis, as defined in the corresponding parts of EN Design effects of actions shall take into account additional requirements that are given in the corresponding parts of EN 1998 to fulfil capacity design principles. Actions applied to the devices and their connections to the structure in the different design situations, including the seismic situations, shall be the basis for the design requirements of the devices and their connections to the structure. 4.3 Conceptual design of the devices Reliability of the devices behaviour NOTE 1 An adequate reliability in the behaviour of the devices and their connections to the structure over their service life, as required in , is necessary in order to reduce the uncertainties inherent in seismic design. Device components shall comply with the relevant European standards. NOTE 2 In the cases where European Standards do not exist, national standards may apply. Choice of the material and construction techniques of the device and its connections to the structure shall be consistent with the design requirements determined for the structure. A good reproducibility of the mechanical behaviour of the device and of its components shall be obtained, as defined in the relevant sections. The description of the mechanical behaviour of the device and its connections to the structure shall be based on adequate modelling and tests, as required in 4.6 and

20 The relevant mechanical and physical properties of the device and its connections to the structure or their components shall be assessed by laboratory tests through appropriate procedures, as required in 4.6 and 4.7 and in the corresponding parts of this European Standard. NOTE 3 Beyond the design seismic action, including reliability factors, there should be no immediate risk of catastrophic failure of the device Capacity design An over-strength factor γ Rd shall be applied to the actions transmitted to the connections between the device and the structure. NOTE The values of γ Rd are defined in the corresponding sections of this European Standard Maintenance All devices and their connections to the structure shall be accessible for inspection and maintenance. NOTE This may be under the responsibility of the designer of the structure. A periodic inspection and maintenance programme for the devices and their connections shall be elaborated during the project implementation Modification and replacement of devices Modification of devices and associated components shall conform to relevant clauses of this European Standard. Otherwise, such modification shall not be permitted. Devices used for replacement shall comply with this European Standard and with additional requirements originally defined by the Owner, unless otherwise requested by him at the time of the replacement. Inspection and maintenance procedures defined in shall be updated as necessary Device documentation The documentation shall indicate the type of the device, its performance and the range of temperature and other environmental conditions specified for the project under consideration. The documentation shall indicate details, sizes and tolerances related to installation of the devices and their connections to the structure, and shall refer to this European Standard. The documentation shall include design checks and results of the relevant type tests and factory production control tests of the devices used in the project. The documentation shall indicate aspects of particular importance for the installation of the devices at their location in the structure. The documentation shall contain a detailed description of inspection and maintenance procedures as required in or in the corresponding parts of this European Standard. The documentation shall contain the description of replacement procedures for the device. NOTE Part of these documents may be provided by the designer of the structure, the remainder being provided by the manufacturer. 19

21 4.4 General properties Material properties Materials used in the design and construction of the devices and their connections to the structure shall conform to existing European Standards where appropriate. NOTE In the cases where European Standards do not exist, national standards or other specifications may apply. Material properties shall be appropriately assessed so as to represent their behaviour adequately under the conditions of strain and strain rate which can be attained during the design seismic situation. Material properties shall take into account the environmental (physical, biological, chemical and nuclear) conditions with which devices can be faced over their service life. In particular, the effects of temperature variation shall be properly taken into account. Material properties shall take into account the ageing phenomena that can occur during the service life of the device. Materials properties shall be represented by representative values Device properties to be used in the analysis Device properties shall take into account the loading history and the accumulated strain cycles. Device properties shall be appropriately assessed so as to represent their behaviour adequately under the conditions of deformation and deformation rate which can be attained during the design seismic situation. Device properties shall take into account the environmental (physical, biological, chemical and nuclear) conditions with which devices can be faced over their service life. In particular, the effects of temperature variation shall be properly taken into account. Device properties shall take into account the ageing phenomena that can occur during the service life of the device. Design (mean) properties (DP) shall be derived from the type tests. Two sets of design properties of the system of devices shall be properly established: Upper bound design properties (UBDP), Lower bound design properties (LBDP). The overall variations of device properties shall lie between the Lower Bound and the Upper Bound. The lower bound shall correspond to the minimum representative value in the conditions where lower values of properties are obtained. The Upper Bound shall correspond to the maximum representative value in the conditions where upper values of properties are obtained. Both bounds shall be obtained by considering the quasi permanent values of the variable actions, as defined in the seismic combinations of actions, according to EN LBDP and UBDP of a given property are representative values obtained from testing procedures defined in the corresponding clauses of this European standard. The ratio between upper bound and lower bound representative values of any performance related device properties shall not exceed the limits defined in the relevant clauses. 20

22 The lower and upper bound representative values shall be determined from the type tests and the following variations: supply temperature ageing ±20% (unless a lower variability has been agreed for the acceptance tests); varying between T U and T L (being the upper and lower values of the temperature considered in the design seismic situations with due regard to quasi-permanent values of the temperature), as in EN 1990; consistent with the service life considered. Combination factors shall be those considered in the seismic combinations of actions. NOTE 1 Specific phenomena, such as low temperature crystallisation, have to be considered. They are dealt with in the corresponding clauses. NOTE 2 According to EN :2004, 10.8(1)P and EN :2005, (3)P and (4)P, the structural analysis takes into account the extreme situations resulting from the consideration of all upper bound design properties (UBDP) and lower bound design properties (LBDP) Re-centring capability In the case of an equivalent linear analysis, to ensure adequate re-centring capability of a seismically isolated structure, it shall be verified that, for a deformation from 0 to d bd : where: E s 0,25 E h (6) E s is the reversibly stored energy (elastic strain energy and potential energy) of the isolation system, including those elements of the structure influencing its response; E h is the energy dissipated by the isolation devices. In the cases where a time history analysis is performed, the most unfavourable value of the considered effect shall be retained from each time history. Then the design value of the action effect shall be deduced from the results obtained from the different time history analyses, according to EN , A common position between TC 340 and TC 250-SC 8 has not yet been agreed upon this subject as of the time this document is being completed and disseminated (June 16 th, 2006). In fact, TC 250-SC 8 will meet on June 23 rd to examine a proposal tendered by a group of experts from TC 340 during a meeting held in Rome on May 18 th The response to the aforesaid TC 250-SC8 will be discussed during the 8 th Meeting in Paris. NOTE According to EN , this rule also applies to the design of the structure. See also B.8 for more details. 21

23 4.5 Constitutive laws The structural analysis shall be based on the appropriate constitutive laws of the devices established by tests as required in 4.6 and 4.7 or in the relevant clauses of this European Standard, so that the behaviour of the structure in the seismic situation may be properly predicted. The behaviour of the devices shall be appropriately modelled to account for non-linear effects as well as any other effects, for instance, those due to velocity dependence or restraints. NOTE For the devices considered, some guidance on modelling constitutive laws is given in the corresponding clauses of this European Standard. 4.6 Validation of anti-seismic devices Any type of device shall be subjected to a technical validation procedure, which shall include elements proving that the device conforms to its functional requirements. It shall prove that the device will remain operational within its domain of use, including the seismic situation, over its lifetime. It shall include at least the following: a description of the ranges of parameters relevant for the type of device under consideration covered by the validation procedure; a method to estimate the expected lifetime; proof of the device s ability to function in a reliable and stable way during its lifetime; values of the mechanical properties of the device, as defined in 4.4; range of acceptable environmental conditions; description of the behaviour beyond design seismic action to determine the γ m values; description of suitable constitutive laws for analysis; a constitutive model describing the behaviour of the device under different conditions of use, including all combinations of actions as defined in EN 1990, representative of the physical phenomena which are expected during the lifetime, notably during the seismic movement; NOTE The influence of the interaction with adjacent structural elements should be taken into account. type tests, as required in below, covering the anticipated ranges of use of the relevant parameters. A validation file, including all the elements gathered in the validation procedure, shall be presented for the device. It shall include at least a list of its properties and a description of the device, of its domain of use, of its constitutive laws, of the calculation model when attached to a structure, and of the associated detailing. It shall include all information related to geometrical, physical, biological, chemical and mechanical characteristics and tolerances. 4.7 Tests Type tests Type tests shall be required: for the validation of new devices, for the validation of existing devices, when materials are changed, 22

24 for the validation of existing devices in ranges of use outside those previously validated, as specified in the relevant clauses of this European Standard. All mechanical properties of the devices needed in the design for the anticipated service lifetime of the system, together with their ranges of variation due to causes as given in 4.4.1, shall be determined by the type tests. Full-scale devices shall be required for these tests, unless otherwise specified in the relevant clauses of this standard. These tests shall include at least cycling tests, in the conditions of use in the seismic design situation, unless otherwise specified in the relevant clauses of this European Standard. Tests shall be done to establish the representative values of the properties. The test report shall include at least the following items: a) Identification of the devices or test specimens (name of manufacturer, origin and number of device manufacturing batch). b) Dimensions, shape and arrangement of the devices or specimens. c) Date, type of test, its duration and any other relevant test conditions. d) Description of test equipment. e) Complete continuous graphical record of test results, where applicable. f) Description of the condition of the device or test specimen prior to and after testing. g) Any operating details not considered in this European Standard and any abnormal incidents occurring during the test. h) Statement that the test was performed in accordance with this European Standard Factory production control tests Factory production control tests shall be performed, before putting the devices into place, to confirm that their properties conform to the design values, within the accepted tolerance. Factory production control tests, manufacturing tolerances and installation shall be defined in the validation file. Detailed description of the factory production control tests according to the type of device considered is given in the corresponding clauses of this European standard. 5 Rigid connection devices NOTE Rigid connection devices are used to constrain movements in one or more directions. Therefore, in principle they do not possess any horizontal distortion capability. However, some deformations are unavoidable and are subjected to the requirements specified under this clause. 5.1 Permanent Connection Devices Permanent connection devices (PCD) shall allow vertical movements and rotations, i.e. shall not transmit vertical loads and bending moments. Moveable connection devices shall restrain movements in one direction only. Fixed connection devices shall restrain movements in two directions. The various elements of permanent connection devices shall be designed and manufactured in accordance with the relevant clause of this European Standard and pren

25 Loads, load effects and load combinations shall be determined in accordance with the Eurocode series and shall be specified in accordance with EN :2000, Annex B. 5.2 Fuse Restraints Performance requirements Fuse restraints (FRs) or sacrificial restraints are devices that, below a certain pre-established force threshold (break-away force), impede any relative movements between connected parts, whereas they freely permit the same after the aforesaid threshold has been exceeded. FRs can be of the mechanic type (MFRs) (when transition is determined by the break-away of sacrificial restraints) or hydraulic in nature (HFRs) (when transition is governed by the opening of an overpressure valve). NOTE Fuse restraints are typically used to control the transition between the service and seismic load condition. They connect in a rigid manner two structural components in order to avoid relative displacement for service load condition, but above a preset force threshold they disconnect the above-mentioned structural components. In this way, they are used to bypass the seismic protection system under service conditions, but leave it free to work during the design earthquake. In order not to modify the behaviour of the isolation and/or damping system, FRs are commonly characterized by a sudden transition from service to seismic load condition Material properties General In addition to the requirements in the following sub-clauses the materials shall be selected for their compatibility with the expected temperature range of the structure Materials Fuse restraints shall be manufactured from ferrous or non-ferrous materials in accordance with the relevant European standards Structural Fasteners Specification and certification of material shall correspond to the requirements referring to stressing and weldability. All materials used shall comply with ISO Welding Welding shall comply with EN 287, EN Design requirements FRs shall be designed to withstand service loads with no yielding or failure. FRs shall be designed so that the maximum design deformation is not exceeded. NOTE 1 FRs, according to the requirements of a particular application, may have to be designed in order to withstand fatigue loads. FRs shall be designed to operate within the design load tolerance t d. For FRs design purposes, the operating load shall not be factored. 24

26 NOTE 2 For the design of the MFR s failing component (sacrificial element) and the set-up of the HFR s overpressure valve, any over-strength factor is not applicable (unfactored load). Over-strength factors are applicable to all the other components of the FR units. Clause does not apply to FRs. After failure, FRs shall not interfere with functioning of anti-seismic devices (if any) Prototype Testing Service Load Test The FR shall be subjected for three times to a monotonically imposed load up to the maximum service load. No yielding or failure shall occur. Among the three cycles, the maximum measured deformation corresponding to the maximum service load shall be less than or equal to the design one Fatigue Test This fatigue test shall be performed when requested by the Design Engineer. The FR shall be subjected to 2 million cycles at the expected level of fatigue load. No yielding or failure shall occur. In order to verify that the fatigue effect is not influencing the FR strength resistance, the test described in and shall be performed on two samples, one subjected to the fatigue load and one not subjected to fatigue load history Break-away Test The FR shall be subjected to a monotonically imposed load up to its break-away load. The SR shall fail within the design load tolerance t d to be given by the design engineer. NOTE In absence of different tolerance limits provided by the Design Engineer, a typical tolerance limit of ±15% is recommended Factory production control tests If the raw material used for the production does not come from the same batch as used for manufacture of the prototypes, it shall be shown by calculation that the design load tolerance is not exceeded when the actual material batch properties are applied. 5.3 Temporary (dynamic) connection devices Functional requirements Within the tolerances specified by the Design Engineer, the Temporary Connection Devices (TCDs), commonly referred to as Shock Transmission Units (STUs), shall provide for an output force in either tension or compression that complies with the design displacement requirements provided by the Design Engineer when the activation velocity is exceeded. In the presence of thermally induced or other slowly imposed movements, the STU shall develop a reaction force less than 10% of its design force, or a lower value as specified by the Design Engineer. NOTE 1 The above requirement is aimed at avoiding fatigue load transmission to the structure. 25